Field of the Invention
The present invention relates to a base film-forming composition, and a directed self-assembly lithography method.
Discussion of the Background
Miniaturization of various types of electronic device structures such as semiconductor devices and liquid crystal devices has been accompanied by demands for miniaturization of patterns in lithography processes. At present, although fine resist patterns having a line width of about 90 nm can be formed using, for example, an ArF excimer laser, further finer pattern formation is required.
To meet the demands described above, a self-assembly lithography process in which a phase separation structure by directed self-assembly, as generally referred to, is utilized that spontaneously forms an ordered pattern has been proposed. As such a directed self-assembly lithography process, a method for forming an ultrafine pattern by directed self-assembly has been known in which a block copolymer is used which is obtained by copolymerizing a monomer compound having one property with a monomer compound having a property that is distinct from the one property (see Japanese Unexamined Patent Application, Publication No. 2008-149447, Japanese Unexamined Patent Application (Translation of PCT Application), Publication No. 2002-519728, and Japanese Unexamined Patent Application, Publication No. 2003-218383). According to this method, annealing of a film containing the block copolymer results in a tendency of clustering of polymer structures having the same property, and thus a pattern can be formed in a self-aligning manner. In addition, a method of forming a fine pattern by permitting directed self-assembling by using a composition that contains a plurality of polymers having properties that are different from one another has been also known (see US Patent Application, Publication No. 2009/0214823, and Japanese Unexamined Patent Application, Publication No. 2010-58403).
In such a directed self-assembly lithography process, it has been known that a phase separation through the aforementioned directed self-assembling may efficiently occur by providing on other layer, a film containing a component such as a polymer to be subjected to directed self-assembling. The layer has been diversely investigated, and it would be reportedly possible to form a variety of phase separation structures by appropriately controlling the surface free energy of the layer when directed self-assembling is allowed by using the block copolymer (Japanese Unexamined Patent Application, Publication No. 2008-36491 and see Japanese Unexamined Patent Application, Publication No. 2012-174984).